Complete: The consequences of virus yellow strain variation on future virus resistant or tolerant sugar beet

Final report

Virus yellows disease is a major threat to the UK sugar beet industry, reducing yields in sugar beet crops by up to 47%. Reductions in available chemical control options, and a shift to reduce the environmental impact of farming practices, means virus yellows-resistant varieties are now seen as the most sustainable and long-term solution. Progress is being made by European sugar beet breeders in the development of such sugar beet varieties, however our understanding of the diversity of strains which may challenge these varieties in the field remains limited. A three-year survey, utilising next generation sequencing of small RNAs and conducted across sugar, fodder, and sea beet plants, identified Beet chlorosis virus (BChV) as more prevalent than Beet mild yellowing virus (BMYV) in symptomatic plants – a finding which goes against previous research but supports more recent studies conducted in France. Further analysis of this sequencing data showed genetic variation within the yellowing virus species. The resilience of resistant varieties to infection with differing virus isolates was then determined. Various plant growth facilities were trialled to establish their suitability for phenotyping the performance of sugar beet varieties under virus infection. The results of these trials indicated that varieties developed against BMYV also performed well under BChV infection, however sugar yield could not be determined under controlled environment conditions. Novel field trials, challenging susceptible and resistant sugar beet varieties with six differing virus isolates were conducted in 2022 and 2023. The results of these trials indicated that despite differences in pathogenicity between virus isolates, the resistant varieties tested proved to have a robust resistance mechanism Suzannah Harder has successfully completed her PhD. Please contact BBRO to view her thesis.